JP59-166752A discloses a technology capable of enlarging a usable speed ratio range and improving fuel economy performance and acceleration performance of a vehicle equipped with a continuously variable transmission (hereinafter, referred to as “CVT”) by searching a maximum value (hereinafter, referred to as “mechanical Low”) and a minimum value (hereinafter, referred to as “mechanical High”) of a speed ratio in which a shift is actually possible in the CVT, using the searched values as target speed ratios for shift control when the searched mechanical Low and High exceed speed ratios set to have a narrower speed ratio width than that based on the design of pulleys used in a shift control and learning actually possible speed ratios for the individual CVT by executing the shift control for the CVT.